JP2000291750A - Chain tensioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To contrive reduction in a work cost and assembly cost of a chain tensioner. SOLUTION: This chain tensioner is formed with a fitting recessed part 13 having a pair of flat surfaces 13a in the internal periphery in a blocked end face of a cylinder chamber 12 formed in a housing 11. A plunger 15 is slidably inserted in the cylinder chamber 12, a screw rod 18 engaged by a screw with an internal thread 17 of this plunger 15 is pressed toward the blocked end of the cylinder chamber 12 by a spring 22. A rod seat 27 receiving a rear end of the screw rod 18 is assembled in the blocked end face of the cylinder chamber 12. A fitting protruded part 28 is provided in the rod seat 27, a pair of engaging surfaces 28a formed in an external periphery of this fitting protruded part 28 are engaged with the flat surface 13a, so as to lock a turn of the rod seat 27, and work for its turn lock part eliminates necessity for high accurate work. In this way, reduction of a cost of work is attained, also generation of press fit powder, when the rod seat 27 is assembled, is prevented, and reduction of cost of assembly is attained by eliminating necessity for washing work.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chain tensioner for maintaining a constant tension of a camshaft driving chain.

[0002]

2. Description of the Related Art A chain tensioner shown in FIG. 5 is known as a chain tensioner for keeping the tension of a chain for driving a cam shaft constant. This chain tensioner has a housing 40
A plunger 42 and a spring 43 are incorporated in a cylinder chamber 41 formed in the cylinder 4.
4 is pressed.

[0003] An oil supply passage 46 communicates with a pressure chamber 45 formed at the back of the plunger 42.
When the plunger 42 moves outward and the pressure in the pressure chamber 45 decreases, the check valve 47 is opened, and oil is driven from the oil supply passage 46 to the pressure chamber 45 by driving the oil supply pump. I try to make it.

In a camshaft driving chain, when the engine is stopped, the chain 44 may be held in a tensioned state due to a stop position of a cam provided on the camshaft. In this case, since the plunger 42 of the chain tensioner is pushed by the tensioned chain 44, the oil in the pressure chamber 45 leaks from the sliding surface of the plunger 42 and the cylinder chamber 41, and the plunger 42 retreats, The elasticity and the tension of the spring 43 are held at a position where they are balanced.

For this reason, when the chain 44 becomes loose due to the restart of the engine, the plunger 42 largely moves outward. At this time, since the hydraulic pump is just after starting and the discharge amount is small, it is not possible to supply sufficient oil to the pressure chamber 45, air enters the pressure chamber 45, damping characteristics are reduced, and abnormal noise is generated. May occur.

Also, at the time of low temperature starting, the viscosity of the oil is high,
Poor fluidity causes the same problems as described above.

In order to solve the above-mentioned problems, a rod insertion hole is formed in the plunger at the rear end face thereof, and a female screw provided on the inner periphery of the opening of the rod insertion hole is formed on the outer periphery of the screw rod. The present patent application filed a chain tensioner in which a male screw and a female screw were engaged with each other, the threads of the male screw and the female screw were formed in a sawtooth shape, and a spring was incorporated between the opposed portions of the plunger and the screw rod to press both members in opposite directions. One has already proposed (Japanese Patent Application No. 9-71947).

In the above chain tensioner, when the engine is stopped and the chain is tensioned due to the cam stop position and a pushing force is applied to the plunger, the pushing force is received by the pressure side flank of the serrated thread. This prevents the plunger from retreating. For this reason, even if the engine is restarted and the slack occurs, the amount of the slack is small, so that the plunger does not largely move outward, thereby preventing the air from entering the pressure chamber. are doing.

[0009]

By the way, in the chain tensioner which has been already proposed, in order to prevent abrasion due to contact with a screw rod to which an axial load is applied and rotational force is applied, a cylinder chamber is provided. A rod sheet is incorporated at the closed end to receive the rear end surface of the screw rod. In this case, when the rod sheet rotates due to the contact with the screw rod, the closed end of the cylinder chamber is worn, so it is necessary to stop the rod sheet from rotating.

Therefore, in the chain tensioner that has been proposed, the rod sheet is attached to the cylinder chamber by press-fitting to prevent rotation, but in this case, the fitting portion between the cylinder chamber and the rod sheet needs to be processed with high precision. Therefore, the processing cost is high, and press-fitting powder is generated at the time of press-fitting, so that cleaning is required after assembling, and the assembling cost is high. Therefore, there is a point to be improved in reducing these costs.

An object of the present invention is to reduce the cost of the chain tensioner already proposed.

[0012]

In order to solve the above-mentioned problems, according to the present invention, a cylinder chamber is provided in a housing, and the cylinder chamber is parallel to an inner periphery of a fitting recess formed in a closed end face of the cylinder chamber. A pair of flat surfaces and a cylindrical surface are provided, an oil supply passage opening in the cylindrical surface is formed in a peripheral wall of the fitting concave portion, and a plunger for pressing a chain is slidably inserted into the cylinder chamber. A female screw is provided on the inner periphery of the opening of the rod insertion hole that opens at the rear end face, a screw rod is screw-engaged with the female screw, and the screw is pressed in the rod insertion hole toward the closed end of the cylinder chamber. And inserted into the fitting recess into a rod sheet that is incorporated into the closed end of the cylinder chamber and receives the rear end of the screw rod, and is inserted between the bottom surfaces of the fitting recess. A fitting projection that forms a gap, and a passage that penetrates the receiving surface that receives the rear end of the screw rod from the end face of the fitting projection, and engages the flat surface on the outer periphery of the fitting projection. A configuration is employed in which a flat surface forming an oil passage is formed between the engagement surface and the cylindrical surface.

According to the above construction, the rod sheet can be prevented from rotating by the engagement between the flat surface of the fitting concave portion and the engaging surface of the fitting convex portion. Since high-precision processing is not required for the formation, and no press-fitting powder is generated at the time of fitting, cleaning work after assembly is unnecessary, and processing cost and assembly cost can be reduced.

Further, by fitting the fitting protrusion of the rod sheet into the fitting recess of the cylinder chamber, it is possible to secure a passage for introducing hydraulic oil between the fitting portions. The size can be reduced.

Here, if the two-face width of the engaging surface formed on the fitting protrusion of the rod sheet is equal to the two-face width of the flat face, the fitting recess is formed even when the rod sheet is rotated by 90 °. Since the fitting projections can be fitted, restrictions on the mounting direction of the rod sheet are reduced, and the mounting can be facilitated.

The manufacturing cost can be reduced by forming the fitting concave portion and the rod sheet by molding. In this case, the rod sheet may be formed of a sintered metal.

If a check valve for preventing the hydraulic oil in the cylinder chamber from flowing back to the oil supply passage side is installed in the passage of the rod seat, the axial load applied to the plunger by the hydraulic oil in the cylinder chamber is reduced. Thus, a chain tensioner having an excellent damper effect can be obtained.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 1, a chain 5 is stretched between a sprocket 2 attached to an end of a crankshaft 1 and a sprocket 4 attached to an end of a camshaft 3, and a slack side of the chain 5 The slipper 6 is in contact with the chain 5a. The slipper 6 is supported swingably about a shaft 7. The slipper 6 is pressed by the chain tensioner 10, and the pressing keeps the chain 5 at a constant tension.

As shown in FIGS. 2 (I) and (II), the chain tensioner 10 has a housing 11 which is screwed to an engine block. A cylinder chamber 12 is formed in the housing 11, and a fitting recess 13 is provided on a closed end face of the cylinder chamber 12.

A pair of flat surfaces 13a parallel to each other and a pair of cylindrical surfaces 13b are provided on the inner periphery of the fitting recess 13. An oil supply passage 14 penetrating from the outer peripheral surface to one cylindrical surface 13b is formed on the peripheral wall of the fitting concave portion 13.

A plunger 15 is slidably inserted into the cylinder chamber 12. A rod insertion hole 16 is formed in the plunger 15 at its rear end face. A male screw 19 formed on the outer periphery of a screw rod 18 is screwed into a female screw 17 provided on the inner periphery of the opening of the rod insertion hole 16. I have.

The screw rod 18 has a spring receiving hole 20 extending axially from the front end and a communication hole 21 penetrating from the rear end to the spring receiving hole 20.
A spring 22 and a spring seat 23 are incorporated between the closed ends of the spring storage hole 20 and the rod insertion hole 16. The spring seat 23 is carburized and quenched, and the spherical surface 24 formed at the tip is provided with the rod insertion hole 16.
Point contact with the closed end of the

The female screw 1 formed on the plunger 15
7 and the thread of the external thread 19 provided on the screw rod 18 have a serrated shape in which the flank angle of the pressure side flank 25 receiving the pushing force when the plunger 15 is pushed in the axial direction is larger than the flank angle of the play side flank 26. It has been. The serrated thread is provided with a lead angle at which the screw rod 18 rotates toward the closed end of the cylinder chamber 12 while rotating by the pressing of the spring 22.

If the female screw 17 is provided by abutment or fixation of a separate nut made of stainless steel or the like at the rear end of the plunger 15, the screw characteristics are improved.

At the closed end of the cylinder chamber 12, a rod sheet 27 for receiving the rear end of the screw rod 18 is incorporated.

As shown in FIGS. 2 and 3, the rod sheet 27 has a fitting projection 28 fitted into the fitting recess 13;
A passage 29 is provided from the end surface of the fitting projection 28 to a receiving surface for receiving the rear end of the screw rod 18.

The length of the fitting projection 28 in the axial direction is the fitting recess 13.
And a gap 30 is provided between the end surface and the bottom surface of the fitting recess 13. A pair of flat engagement surfaces 28a and a pair of flat surfaces 28b are alternately formed on the outer periphery of the fitting projection 28 in the circumferential direction.
8b is provided with an arc surface 28c.

The engagement surface 28a is a flat surface 13 of the fitting recess 13.
a to prevent the rod sheet 27 from rotating. On the other hand, the flat surface 28b is opposed to the cylindrical surface 13b of the fitting recess 13 to form an oil passage 31 between the opposed surfaces, and the arc surface 28c is fitted to the cylindrical surface 13b.

The width W ₁ of the pair of engagement surfaces 28a of the rod sheet 27 is equal to the width W ₂ of the pair of flat surfaces 28b.
_{As in the case of 2} , the fitting projection 28 of the rod sheet 27 can be fitted into the fitting recess 13 of the cylinder chamber 12 even when the rod sheet 27 is rotated by 90 °.

The rod sheet 27 is made of sintered metal and is formed by molding. The cylinder chamber 1
The second fitting recess 13 is also formed by die molding or the like.

A spring 32 is provided between the rod seat 27 and the plunger 15 to give the plunger 15 an outward projecting property. When a check valve described later is provided, the spring 32 may be omitted.

Now, when the engine is started and the sprocket 2 attached to the end of the crankshaft 1 rotates in the direction of the arrow, the slack side chain 5a of the chain 5 is slackened. And pressure of the hydraulic oil fed into the passage 29 and the spring 3
2, the plunger 15 and the screw rod 18 move outward, and the screw rod 18 separates from the rod sheet 27 by the movement, and the cylinder chamber 1
2 is supplied with oil.

When the plunger 15 moves outward, the plunger 15 presses the slipper 6, so that the slack of the chain 5 is absorbed and the screw rod 18 is rotated by the elastic force of the spring 22 while the cylinder is rotated. The plunger 15 moves toward the closed end of the chamber 12 and abuts against the rod sheet 27, and the plunger 15 and the screw rod 18
Stops, the chain 5 is maintained at a predetermined tension.

When the temperature of the engine rises, the center distance between the crankshaft 1 and the camshaft 3 increases due to thermal expansion, and the plunger 15 is pressed by the increased tension of the chain 5, the pressing force is applied to the cylinder chamber 12. The plunger 15 is received by the enclosed hydraulic oil and the spring 32 and received by the pressure side flank 25 of the female screw 17 and the male screw 19, so that the plunger 15 does not retreat. When the pressing force for pressing the plunger 15 becomes stronger than the combined force of the elasticity of the springs 22 and 32 and the hydraulic pressure, the screw rod 18
Rotates, and the plunger 15 retreats.

At this time, the operating oil in the cylinder chamber 12 is
Leakage occurs between the sliding surfaces of the cylinder chamber 12 and the plunger 15, and the plunger 15
Slowly retreats to a position where the elasticity of the oil and the resultant force of the pressure of the supply oil are balanced.

When the engine is stopped, the slack side chain 5a of the chain 5 may be tensioned due to the stop position of the cam provided on the camshaft 3. In this case, the plunger 15 is pressed by the chain 5, and the pressing force is received by the pressure side flank 25 in the screw engagement portion between the female screw 17 and the male screw 19.

Since the pressing force is a static load without vibration, the screw rod 18 does not rotate even when the pressing force is greater than the elasticity of the spring 22.
The plunger 15 does not retreat.

Therefore, even if the slack side chain 5a of the chain 5 is slackened due to the restart of the engine, the slack amount is extremely small, and the protruding amount of the plunger 15 is also small. Therefore, since the pressure drop in the cylinder chamber 12 is small, air does not enter the cylinder chamber 12, and it is possible to prevent the disadvantage that the damping characteristics are reduced.

When the engine is started at a low temperature, the viscosity of the oil sent from the pump to the oil supply passage 14 is high, and
The flow of hydraulic oil to the cylinder chamber 2 is poor, but even in this case, since the amount of outward movement of the plunger 15 is small, the cylinder chamber 1
2 can be prevented from entering the air.

The rod sheet 27 which receives the rear end of the screw rod 18 has a pair of flat surfaces 13a which
And a pair of engagement surfaces 28a formed on the inner periphery of
Since the rod sheet 27 is prevented from rotating by the fitting of the fitting projections 28 formed on the outer periphery of the rod sheet 27, it is necessary to form the fitting recesses 13 and the fitting projections 28 with high precision. Instead, the fitting concave portion 13 and the fitting convex portion 28 are formed only by molding, so that cutting is not required, and the processing cost can be reduced.

Further, since the rod sheet 27 can be prevented from rotating by inserting the fitting projection 28 into the fitting recess 13, no press-in powder is generated. For this reason, the cleaning work after assembling the rod sheet 27 can be made unnecessary, and the press-fitting step can be eliminated and the assembling cost can be reduced.

The flat surface 28 b formed on the outer periphery of the fitting projection 28 of the rod sheet 27 is fitted to the fitting recess 1 of the cylinder chamber 12.
Oil passage 31 between a cylindrical surface 13b provided on the inner circumference of
The oil passage 31 communicates with the rear end face of the fitting projection 28 and the gap 30 formed on the bottom surface of the fitting recess 13,
The operating oil from the oil supply passage 14 is supplied to the passage 2 of the rod sheet 27.
9, there is no need to provide an introduction path in the end wall of the fitting recess 13, and the housing 1
1 can be reduced in size in the axial direction.

As shown in the embodiment, the rod sheet 2
7, a pair of engagement surfaces 28a formed on the outer periphery of the fitting projection 28.
When the flat plate-W ₁ and equal to width across flats W ₂ of the pair of flat surfaces 28b, the fitting convex portion 28 in the fitting recess 13 of the cylinder chamber 12 even in a state where the rod seat 27 is rotated 90 ° Insert Therefore, the rod sheet 27 can be easily assembled.

FIG. 4 shows another example of the chain tensioner 10 according to the present invention. The chain tensioner 10 in this example and the chain tensioner 1 shown in FIG. 2 described above.
0 means that the cylinder chamber 12
The difference is that a check valve 33 for preventing the working oil in the inside from flowing back to the oil supply passage 14 side and a retainer 34 for limiting the opening and closing amount of the check valve 33 are incorporated.

As shown in FIG. 4, by incorporating the check valve 33 in the passage 29 of the rod seat 27, the axial load applied to the plunger 18 by the hydraulic oil in the cylinder chamber 12 can be received. A highly effective chain tensioner can be obtained.

[0047]

As described above, according to the present invention, the fitting recess is formed at the closed end of the cylinder chamber, and the rod sheet is provided with the fitting protrusion fitted to the fitting recess. Since a pair of engagement surfaces that engage with a pair of flat surfaces formed on the inner periphery of the fitting concave portion are provided on the outer periphery of the fitting convex portion to prevent the rod sheet from rotating, the fitting concave portion and the fitting convex portion Since high-precision processing is not required for both, the processing cost can be reduced, and no press-in powder is generated when the fitting projection is fitted to the fitting recess. The operation can be eliminated, and the assembly cost can be reduced.

Further, by providing a flat surface which forms an oil passage between the fitting convex portion and the cylindrical surface of the fitting concave portion on the outer periphery of the fitting convex portion, it is possible to supply oil between the fitting concave portion and the fitting portion of the fitting convex portion. Since the introduction path for guiding the hydraulic oil from the passage to the passage of the rod sheet can be ensured, the axial length of the housing can be reduced in size.

Further, by incorporating a check valve in the passage of the rod seat, a chain tensioner having an excellent damper effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a front view showing a use state of a chain tensioner according to the present invention.

FIG. 2 (I) is a cross-sectional plan view of the chain tensioner shown in FIG. 1, and FIG. 2 (II) is a cross-sectional view taken along line aa of FIG. 1 (I).

FIG. 3 is a perspective view showing a rod sheet of the chain tensioner shown in FIG. 2;

FIG. 4 is a partially cutaway plan view showing another example of the chain tensioner according to the present invention.

FIG. 5 is a longitudinal sectional front view showing a conventional chain tensioner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Housing 12 Cylinder chamber 13 Fitting recess 13a Flat surface 13b Cylindrical surface 14 Oil supply passage 15 Plunger 16 Rod insertion hole 17 Female screw 18 Screw rod 22 Spring 27 Rod seat 28 Fitting recess 28a Engaging surface 28b Flat surface 31 Oil passage 33 Check valve

Claims (5)

[Claims] 1. A cylinder chamber is provided in a housing, and a pair of flat surfaces parallel to each other and a cylindrical surface are provided on an inner periphery of a fitting recess formed in a closed end face of the cylinder chamber. An oil supply passage opening in the cylindrical surface is formed in the peripheral wall of the recess, and a chain pressing plunger is slidably inserted into the cylinder chamber, and a female screw is formed on the inner periphery of the opening of the rod insertion hole opened in the rear end surface of the plunger. A screw rod is screw-engaged with the female screw, and a spring for pressing the screw rod toward the closed end of the cylinder chamber is incorporated in the rod insertion hole, and the screw is incorporated into the closed end of the cylinder chamber. A fitting projection inserted into the fitting recess into the rod sheet for receiving the rear end of the rod, forming a gap between the bottom surfaces of the fitting recess, and a slide from the end face of the fitting projection. A passage that penetrates the receiving surface that receives the rear end of the clew rod is provided. A chain tensioner with a flat surface to be formed. 2. The chain tensioner according to claim 1, wherein the two widths of the engaging surface and the flat surface formed on the fitting projection are the same. 3. The chain tensioner according to claim 1, wherein the fitting recess and the rod sheet are formed by molding. 4. The chain tensioner according to claim 1, wherein said rod sheet is made of a sintered metal. 5. The chain tensioner according to claim 1, wherein a check valve for preventing hydraulic oil in a cylinder chamber from flowing back to an oil supply passage side is incorporated in the passage of the rod seat.